The invention relates generally to apparatus for manufacturing, filling and closing shipping containers made of synthetic plastic material. More particularly, the invention relates to a method for removing undesired residue of a filling liquid which is inserted by means of a filling mandrel into the shipping container as well as to an apparatus suitable for implementing the method.
In known methods for the continuous manufacture of filled, closed hollow containers of thermoplastic material, a tube or hose made of synthetic plastic material which is extruded while still in a plastic state is enclosed within the forming molds for the container which move at the same velocity as the hose. The hose is inflated into the formed shape in this manner by an increased internal pressure, with the resulting container being filled while a connection with the formed container base is maintained, with a subsequent separating and closing operation being performed by welding after which the container is detached. In addition to this generally known process, further improvements have been developed which consist, however, basically only in a supplement and further development of these known techniques. In all prior art proposals thus far, a filling mandrel is basically used which is insertable through an opening in the head of the mold forming the container, or which is already in position within the mold during the shaping or molding process. When, for example, highly viscous fluids are to be used in the filling operation, difficulties occur due to the fact that as a result of increased adhesive forces, residue of the filling liquid tends to adhere to the surface of the filling mandrel thereby causing difficulties in succeeding molding or forming operations of the container causing unwanted separation of portions of the liquid or other materials. This disadvantage is avoided by presently known state-of-the art techniques by removing the filling mandrel from the container during different stages of the process in accordance with the constantly rising fluid level. Thus, only a small part of the filling mandrel is wetted with the liquid. However, such an approach results in a considerable increase in the cost requirements of the apparatus particularly due to the additional control elements which are necessitated by the requirement for introduction and removal of the filling mandrel. A further disadvantage arises in that a considerable delay can occur in a machine which is required to operate continuously because the insertion and removal of the filling mandrel is time consuming and hence causes a reduction in the output of the machine or in its operating efficiency.
The present invention is intended to avoid these disadvantages while at the same time insuring that in a process of the aforementioned type, despite the rigid connection of the filling mandrel, any filling liquid which remains thereon as a residue will not operate to disturb or unduly influence the succeeding molding or shaping operations.